Hydraulic dampers with pressure regulated control valve

ABSTRACT

A suspension damper includes a housing bounding a main chamber. A hydraulic fluid is disposed within the main chamber. A piston rod is selectively movable between an advanced position wherein a portion of the piston rod is advanced into the main chamber and a retracted position wherein the portion of the piston rod is retracted from the main chamber, wherein as the piston rod is moved a fluid pressure of the hydraulic fluid within the main chamber progressively increases and a portion of the hydraulic fluid passes through a passage within the housing. A control valve is at least partially disposed within the main chamber, the control valve being moved by the fluid pressure of the hydraulic fluid so as to progressively restrict the flow of the hydraulic fluid through the passage as the fluid pressure of the hydraulic fluid within the main chamber progressively increases.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/958,149, filed Dec. 17, 2007, which is a continuation ofpatent application Ser. No. 11/228,284, filed Sep. 15, 2005, U.S. Pat.No. 7,308,976, which is a continuation of patent application Ser. No.10/449,722, filed May 29, 2003, U.S. Pat. No. 6,978,872, which claimsthe benefit to U.S. Provisional Application Ser. No. 60/384,369, filedon May 29, 2002, which are incorporated herein by specific reference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to hydraulic dampers which can be usedindependently or as part of a shock absorber, front fork or othersuspension system.

2. The Relevant Technology

Dampers are used in conventional shock absorbers, front forks, and othersuspension systems to dampen or absorb an impact or force applied to thesuspension system. For example, a conventional damper includes a tubularhousing bounding a sealed chamber. An incompressible hydraulic fluid isdisposed within the chamber of the housing. One end of a piston rodhaving a piston mounted thereon is also disposed within the chamber.Orifices extend through the piston so that the piston can slide withinthe chamber of the housing as the hydraulic fluid passes through theorifices.

When a compressive force is applied to the damper, such as when anautomobile having shock absorbers hits a bump, the force seeks to drivethe piston rod into the chamber of the housing. The damper partiallyabsorbs this force by using the force to compress the hydraulic fluidthrough orifices. When a rebound force is applied to the damper, such asthrough the application of a spring, the damper again regulates therebound force by requiring the hydraulic fluid to pass back through theorifices in the piston in order for the piston rod to return to itsoriginal position.

Although conventional dampers impart some degree of damping tosuspension systems, conventional dampers have significant shortcomings.For example, the damping properties of conventional dampers are directlyrelated to the constant restriction of the hydraulic fluid flow throughthe orifices extending through the piston. As this variable does notchange along the stroke of the piston rod, the damping properties aresubstantially constant independent of the force applied or the positionof the piston rod. As a result, minimum damping performance is achieved.That is, what is needed in the art are dampers for suspension systemsthat can automatically adjust the damping characteristics throughout therange of piston movement to more efficiently dampen based on changingoperating and road conditions.

Although attempts have been made to produce adjustable dampers, suchdampers have had minimal effectiveness, are difficult and expensive toproduce, and permit minimal selective adjustment based on use andcondition requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope.

FIG. 1 is a cross sectional side view of one embodiment of a damper;

FIG. 2 is an exploded perspective view the distal end of the piston rodof the damper depicted in FIG. 1;

FIG. 3 is an enlarged cross sectional side view of the components shownin FIG. 2 in an assembled state;

FIG. 4 is a cross sectional side view of the damper shown in FIG. 1 withthe control valve in an open state;

FIG. 5 is a cross sectional side view of the damper shown in FIG. 4 withthe piston rod being advanced into the housing;

FIG. 6 is a cross sectional side view of the damper shown in FIG. 5 withthe piston rod fully advanced into the housing;

FIG. 7 is a cross sectional side view of the damper shown in FIG. 6 withthe piston rod being retracted out of the housing;

FIG. 8 is a cross sectional side view of a spring biased against thefloating piston at the distal end of the damper shown in FIG. 1;

FIG. 9 is a cross sectional side view of an inflated bladder disposed atthe distal end of the damper shown in FIG. 1;

FIG. 10 is a cross sectional side view of a flexible diaphragm disposedat the distal end of the damper shown in FIG. 1;

FIG. 11 is a cross sectional side view of a boundary line between ahydraulic fluid and a compressible gas disposed at the distal end of thedamper shown in FIG. 1;

FIG. 12 is a cross sectional side view of an alternative embodiment of adamper having an adjusting piston;

FIG. 13 is a cross sectional side view of the damper shown in FIG. 12with the adjusting piston moved to a second position;

FIG. 14 is a schematic representation of a remote pressure regulateddampening system;

FIG. 15 is a cross sectional side view of an alternative embodiment of adamper having a fixed control valve assembly;

FIG. 16 is a cross sectional side view of the damper shown in FIG. 15with the piston rod being advanced into the housing thereof;

FIG. 17 is a cross sectional side view of the damper shown in FIG. 16with the piston rod being fully advanced into the housing;

FIG. 18 is a cross sectional side view of the damper shown in FIG. 17with the piston rod being retracted out of the housing;

FIG. 19 is a cross sectional side view of a twin tube damper;

FIG. 20 is a cross sectional side view of the twin tube damper shown inFIG. 19 with the piston rod being advanced into the inner tube thereof;

FIG. 21 is a perspective view of a shock absorber;

FIG. 22 is an elevated front view of the shock absorber shown in FIG.21;

FIG. 23 is a an elevated side view of the shock absorber shown in FIG.21;

FIG. 24 is a cross sectional side view of the shock absorber shown inFIG. 21;

FIG. 25 is a cross sectional view of the shock absorber shown in FIG. 24taken along section lines 25-25;

FIG. 26 is an enlarged cross sectional side view of the second end ofthe stem of the shock absorber shown in FIG. 24;

FIG. 27 is an enlarged cross sectional side view of the gas volumeadjuster assembly of the shock absorber shown in FIG. 24;

FIG. 28 is a cross sectional side view of an alternative embodiment of adamper having a base valve assembly;

FIG. 29 is an enlarged cross sectional side view of the base valveassembly shown in FIG. 28;

FIG. 30 is a cross sectional side view of the damper shown in FIG. 28with the piston rod being advanced in the housing thereof;

FIG. 31 is a cross sectional side view of the damper shown in FIG. 30with the piston rod being retracted from the housing;

FIG. 32 is a cross sectional side view of an alternative embodiment ofthe damper shown in FIG. 28 with the floating piston being replaced by aflexible diaphragm;

FIG. 33 is a cross sectional side view of an alternative embodiment ofthe damper shown in FIG. 28 with the base valve assembly being replacedby an alternative base valve assembly;

FIG. 34 is an elevated cross sectional side view of a front fork with acartridge incorporating a damper of the present invention;

FIG. 35 is an elevated cross sectional side view of the front fork shownin FIG. 34 with the piston rod being advanced into the upper tubethereof;

FIG. 36 is an elevated cross sectional side view of the front fork shownin FIG. 34 with the cartridge removed,

FIG. 37 is an elevated cross sectional side view of the front fork shownin FIG. 36 with the piston rod being advanced into the upper tubethereof;

FIG. 38 is an elevated cross sectional side view of the front fork shownin FIG. 36 with the piston rod being retracted from the upper tubethereof;

FIG. 39 is an elevated cross sectional side view of a front fork havinga fixed base valve in the upper tube; and

FIG. 40 is an elevated cross sectional side view of the front fork shownin FIG. 39 with the piston rod being retracted from the upper tubethereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to hydraulic dampers which can be usedindependently or as part of a shock absorber, front fork or othersuspension system. Such dampers can be used in association with alltypes of vehicles or mechanical apparatus where it is desired to controlsuspension movement and/or vibration. Examples of vehicles on which thedampers can be used include bicycles, motorcycles, automobiles, allterrain vehicles, snowmobiles, airplanes, and the like.

Depicted in FIG. 1 is one embodiment of a damper 10 incorporatingfeatures of the present invention. Damper 10 comprises a housing 12having an interior surface 14 bounding a chamber 16. Housing 12comprises a cylindrical sidewall 18 that extends between a proximal end20 and an opposing distal end 22. An end wall 24 is formed at distal end22 of sidewall 18. A bracket 30 having a hole 32 extending therethroughis formed on end wall 24 for selectively attaching damper 10 to astructure. In alternative embodiments, bracket 30 can be replaced withany conventional attachment structure.

A cap 26 is removably threaded or otherwise attached onto proximal end20 of sidewall 18. Cap 26 has a passageway 28 centrally extendingtherethrough so as to communicate with chamber 16. A piston rod 34 isslideably disposed within passageway 28 so as to extend into and outsideof chamber 16. Piston rod 34 has an exterior surface 36 extendingbetween a proximal end 37 (FIG. 2) and an opposing distal end 38. Anannular seal 40 extends between cap 26 and piston rod 34 so as to effecta sealed connection that enables piston rod 34 to freely slide relativeto housing 12.

Piston rod 34 comprises a base rod 42 and a bolt 44. As depicted in FIG.2, base rod 42 comprises an exterior surface 45 extending between aproximal end 46 and an opposing distal end 48. Distal end 48 terminatesat a distal end face 50. A substantially L-shaped channel 52 (see alsoFIG. 3) extends from distal end face 50 to exterior surface 45 at distalend 48.

Bolt 44 comprises a shaft 56 having a proximal end 58 and an opposingdistal end 60. Proximal end 58 of shaft 56 terminates at a proximal endface 64. As depicted in FIGS. 2 and 3, distal end 60 of shaft 56terminates at a distal end face 66. Encircling and radially outwardlyprojecting from shaft 56 at distal end 60 is a head 70. Head 70 also hasa proximal end face 72 and an opposing distal end face 74. Distal endface 74 of head 70 is spaced proximal of distal end face 66 of shaft 56.A channel 78 extends through shaft 56 from distal end face 66 toproximal end face 64. A plurality of radially spaced apart ports 79extend from channel 78 to distal end face 74 of head 70. Removablythreaded into channel 78 at distal end face 66 of shaft 56 is a jet 80having an opening 82 extending therethrough. For reasons as will bediscussed below in greater detail, jet 80 can be replaced with otherjets having different sized openings. Alternatively, jet 80 can bereplaced with a plug so that the only access to channel 78 at distal end60 of shaft 56 is through ports 79.

One or more flexible metal spring shims 84 are mounted on distal endface 74 of head 70 so as to encircle shaft 56 and cover the openings toports 79. Shims 84 are secured in place by a C-clip 86 mating with agroove on shaft 56 distal of shims 84. In an alternative embodiment,C-clip 86 can be replaced with a washer. Jet 80 can then be formed withan outwardly projecting flange at the end thereof. As jet 80 is screwedinto channel 78, the flange biases the washer against the shims 84 so asto secure shims 84 in place.

During assembly, proximal end 58 of bolt 44 is threaded into distal end48 of base rod 42 so that channels 52 and 78 are in fluid communication.The combination of channels 52 and 78 are herein referred to as reboundchannel 88. In alternative embodiments, it is appreciated that base rod42 and bolt 44 can be integrally formed as a single member. Furthermore,bolt 44 can be replaced with a nut that threads onto the distal end ofbase rod 42.

Depicted in FIG. 2, mounted on distal end 38 of piston rod 34 is a mainpiston 102, a control valve assembly 100, and a stop plate 174. Controlvalve assembly 100 comprises a valve guide 104 and a control valve 106.Main piston 102 has a substantially circular disk shape configurationwith a proximal face 108, an opposing distal face 110, and a peripheralside 112 extending therebetween. A groove 113 is formed on peripheralside 110 so as to receive an annular seal 114 (FIG. 3). In theembodiment depicted, seal 114 comprises a flexible o-ring 96 thatoutwardly biases an annular band 98. Band 98 is typically comprised ofTeflon. Other conventional seal configurations can also be used. It isnoted that in several of the other drawings showing pistons, the annularseal has been not been shown in the peripheral groove. This was done soas to help clarify the drawings. It is appreciated that in use, however,a seal is disposed within each peripheral groove.

A plurality of spaced apart, elongated pressure ports 118 extend throughmain piston 102 from proximal face 108 to distal face 110. Pressureports 118 extend at a substantially constant radius from the center ofmain piston 102. Disposed on proximal face 108 between each adjacentpressure port 118 is an elongated shallow pocket 120. Each pocketextends along a radial axis aligned with the center of main piston 102.Extending from distal face 110 of main piston 102 to each pocket 120 isa corresponding rebound port 122. Rebound ports 122 are disposedradially inward of pressure ports 118. A central opening 116 alsoextends though main piston 102.

In the assembled state depicted in FIG. 3, piston rod 34 is passedthough central opening 116 of main piston 102 so that main piston 102encircles and radially outwardly projects from piston rod 34 proximal ofhead 70. Seal 114 is biased in sealed engagement against interiorsurface 14 of sidewall 18 so as to enable main piston 102 to freelyslide within chamber 16 as piston rod 34 is moved within chamber 16.

In one embodiment of the present invention means are provided forenabling fluid flow through rebound port 122 from proximal face 108 todistal face 110 while precluding fluid flow from distal face 110 toproximal face 108. By way of example and not by limitation, a pluralityof stacked shims 124 encircle piston rod 34 and bias against distal face110 of main piston 102. Stacked shims 124 cover the distal opening torebound ports 122 but do not cover the openings to compression ports118. A washer 126 is disposed between head 70 and stacked shims 124 soas to provide space for the outer perimeter of stacked shims 124 to flexdistally. Fluid can thus travel in a distal direction through reboundports 122 by flexing shims 124, but is precluded from traveling in aproximal direction through rebound ports 122 as a result of shims 124.Shims 124 thus act as a type of one-way check valve during compressivemovement of piston rod 34 and pressure sensitive valves during therebound movement of piston rod 34. That is, the greater the fluidpressure against shims 124 during the rebound stroke, the farther shims124 flex and the more rebound ports 122 are opened.

In alternative embodiments of the means for enabling fluid flow throughrebound port 122, it is appreciated that shims 124 can be replaced withany number of alternative one-way check valve designs. For example,flexible shims 124 can be replaced with a solid washer or hinged flapsthat are biased against distal face 110 over rebound ports 122 by aspring. One such example is discussed below with regard to FIG. 29. Itis noted that there are a number of different elements and alternativedesigns disclosed herein which incorporate flexible shims as a one-waycheck valve. It is appreciated that each such use of shims is intendedto have a corresponding means for enabling fluid flow in a selectdirection and that such shims can be replaced with alternative one-waycheck valve designs as discussed above.

Depicted in FIG. 2, valve guide 104 comprises an annular base 130 havinga proximal face 132 and an opposing distal face 134. Projecting fromdistal face 132 is an annular stem 136. Stem 136 has an outer diametersmaller than the outer diameter of base 130. A central opening 138extends through both stem 136 and base 130. In the assembled statedepicted in FIG. 3, piston rod 34 is passed through central opening 138so that distal face 134 of valve guide 104 rests against proximal face108 of main piston 102. Valve guide 104 only partially covers pockets120 so that fluid communication is still made with rebound ports 122though pockets 120. It is noted that valve guide 104 is locked in placeby being clamped between a shoulder 181 formed on piston rod 34 and mainpiston 102. In alternative embodiments, it is appreciated that valveguide 104 can be directly secured to or integrally formed with mainpiston 102.

Depicted in FIGS. 2 and 3, control valve 106 has an annular peripheralside 144 extending between an annular distal face 146 and an annularproximal face 148. Distal face 146 has a surface area smaller than thesurface area of proximal face 148. In one embodiment, the aspect ratioof the surface area of distal face 146 to the surface area of proximalface 148 is in a range between about 0.3 to about 0.6 with about 0.3 toabout 0.4 being more preferred. In general, control valve 106 comprisesan annular collar 150 having an interior surface 152. An annular flange154 radially inwardly projects from interior surface 152 of collar 150at a proximal end thereof. Flange 154 has a proximal face 155 thatterminates at an interior surface 157. A central opening 156 extendsthrough both collar 150 and flange 154.

In the assembled state, piston rod 34 is slideably received withincentral opening 156 so that control valve 106 slideably mates with valveguide 104. Specifically, in the position depicted in FIG. 3, collar 150of control valve 106 encircles base 130 of valve guide 104. An annulargroove 158 is formed on interior surface 152 of collar 150 and receivesan annular first seal 160. First seal 160 biases against base 130 ofvalve guide 104 so as to form a slideable sealed engagement betweencollar 150 and base 130.

Flange 154 of control valve 106 encircles stem 136 of valve guide 104.An annular groove 162 is formed on interior surface 157 of flange 154and receives an annular second seal 164. Second seal 164 biases againststem 136 of valve guide 104 so as to form a slideable sealed engagementbetween flange 154 and stem 136. It is noted that in several of theother drawings showing control valve assembly 100, first seal 160 andsecond seal 164 are not shown in their corresponding grooves. This wasdone so as to help clarify the drawings. It is appreciated that in use,however, seals 160 and 164 are disposed within their correspondinggrooves in each control valve assembly 100.

An annular groove 166 is also formed on the interior surface of controlvalve 106 between first seal 158 and second seal 164. In part, groove166 bounds a valve chamber 170 formed between control valve 106 andvalve guide 104 and which is sealed closed by first seal 158 and secondseal 164. Disposed within valve chamber 170 is a compressible gas suchas air. In one embodiment, as control valve 106 is received over valveguide 104, air is captured within valve chamber 170 at a first pressure,i.e., atmospheric pressure. In alternative embodiments, it isappreciated that a resiliently compressible member such as a spring orcompressible material can also be disposed within valve chamber 170 soas to bias between valve guide 104 and control valve 106.

As depicted in FIG. 2, annular stop plate 174 has a distal side 176 andan opposing proximal side 178. A central opening 180 and a plurality ofradially spaced apart ports 182 extend through stop plate 174 betweenopposing sides 176 and 178. As depicted in FIG. 3, distal end 48 of baserod 42 is passed through central opening 180 such that stop plate 174 iscaptured between a shoulder 181 of base rod 42 and valve guide 104.

Stop plate 174 functions as a stop for control valve assembly 100.Specifically, control valve assembly 100 operates at various statesbetween an open position and a closed position. In the closed positiondepicted in FIG. 3, distal face 146 of control valve 106 biases againstproximal face 108 of main piston 102 so as to cover the proximalopenings to compression ports 118. However, a portion of pockets 120 onmain piston 102 are not covered by control valve 106 or valve guide 104so that open fluid communication is provided to rebound ports 122through pockets 120. As discussed below in greater detail, it is alsonoted that when control valve 106 is in the closed position, valvechamber 170 is collapsed so as to have a first volume.

Depicted in FIG. 4, control valve assembly 100 is in the fully openposition. In this configuration, control valve 106 has slid proximallyrelative to valve guide 104 so that proximal face 148 of control valve106 is biased against stop plate 174, thereby stopping further proximalmovement of control valve 106. In this open position, control valve 106is spaced apart from main piston 102 so that fluid is free to travelthrough the compression ports 118 and through a flow channel 167 formedbetween control valve 106 and main piston 102. It is also noted that inthe open position, distal face 155 of flange 154 of control valve 106 isspaced apart from proximal face 132 of base 130 of valve guide 104,thereby expanding valve chamber 170 so as to have a second volume thatis lager than the first volume. The pressure in valve chamber 170 isgreater in the collapsed state than in the expanded state. As such, thepressure within valve chamber 170 has the natural tendency to pushcontrol valve 106 into the open position under a force corresponding tothe relative pressure within valve chamber 170.

Returning to FIG. 1, slideably disposed within chamber 16 distal ofpiston rod 34 is a floating piston 184. Floating piston 184 has aperipheral side 186 that extends between a distal face 188 and anopposing proximal face 190. A seal 192 is disposed on peripheral side186. Seal 192 biases in sealed engagement against interior surface 14 ofsidewall 18 of housing 12 so as to enable floating piston 184 toselectively slide within chamber 16 but substantially precluding fluidor gas from passing through or around floating piston 184.

Floating piston 184 divides chamber 16 into a distal compartment 196 anda proximal compartment 198. Compartments 196 and 198 each change inrelative size as floating piston 184 slides within chamber 16. Disposedwithin distal compartment 196 is a compressible gas, such as air, whiledisposed within proximal compartment 198 is a hydraulic fluid. As usedin the specification and appended claims, the term “hydraulic fluid” isintended to include all types of fluids that can be used to transferhydraulic pressures. Although hydraulic fluids are generally consideredas being substantially non-compressible, it is appreciated thathydraulic fluids can be emulsified or have entrained gas, thereby makingthem slightly compressible.

The gas within distal compartment 196 is disposed at a second pressurethat is greater than the first pressure of the gas within valve chamber170. Accordingly, in the static position shown in FIG. 1 with piston rod34 retracted out of chamber 16, control valve 106 is in the closedposition. That is, the pressure within distal compartment 196 istransferred through floating piston 184 and the hydraulic fluid withinproximal compartment 198 so to collapse valve chamber 170 and move valveguide 106 into the closed position.

In general, control valve 106 is closed because of the opposing forcesapplied by the hydraulic fluid on distal side 134 of valve guide 104 andon proximal face 148 of control valve 106. Although not required, it hasbeen empirically determined that control valve assembly 100 moreeffectively operates under the applied pressures to move between theopen and closed positions if the surface area of distal side 134 ofvalve guide 104 is at least 50%, preferably at least 60% and morepreferably at least 70% of the surface area of proximal face 148 ofcontrol valve 106.

During operation, when a force is applied to proximal end 37 of pistonrod 34 which is greater than the force which is maintaining controlvalve assembly 100 in the closed position, piston rod 34 with mainpiston 102 and control valve assembly 100 begin to move distally withinchamber 16. Specifically, as depicted in FIG. 4, as piston rod 34 movesdistally within chamber 16, the hydraulic fluid within proximalcompartment 198 travels through compression ports 118 and pushes againstdistal face 146 of control valve 106, thereby causing control valve 106to at least partially slide into the open position.

Control valve assembly 100 meters the flow of hydraulic fluid throughcompression ports 118 during the advancement of main piston 102. Theextent to which control valve 106 slides distally in part depends on therate and magnitude of the force applied to piston rod 34. For example,if a large force is rapidly applied to piston rod 34, i.e., sharphi-speed bump force, control valve assembly 100 is quickly moved to thefully open position as a result of the high pressures that are producedin proximal compartment 198 and applied to distal face 146 of controlvalve 106. The hydraulic fluid can thus freely travel throughcompression ports 118 and around control valve 106, thereby allowingpiston rod 34 to rapidly and easily advance within chamber 16. As such,the impact of the initial force on piston rod 34 is quickly absorbed bymovement of piston rod 34. In contrast, if a gradual small force isapplied to piston rod 34, control valve 106 is only partially moved tothe open position so that flow passageway 167 remains partiallyconstricted. This constriction of flow passageway 167 decreases the flowof hydraulic fluid through compression ports 118 and thus slows ofmovement of main piston 102 within chamber 16.

As depicted in FIG. 5, as more of piston rod 34 enters proximalcompartment 198, piston rod 34 displaces a corresponding volume of thehydraulic fluid therein. Because the hydraulic fluid does notsignificantly compress, the hydraulic fluid causes floating piston 184to slide distally and compress the gas with distal compartment 196. Asthe gas pressure increases within distal compartment 196, the fluidpressure within proximal compartment 198 increases and the fluidpressure begins to collapse valve chamber 170, thereby moving controlvalve 106 into the closed position. As control valve 106 moves into theclosed position, flow channel 167 constricts making it more difficultfor the hydraulic fluid to pass therethrough. Accordingly, the fartherpiston rod 34 advances into chamber 16, the greater the resistance forcethat is applied against piston rod 34.

As depicted in FIG. 6, piston rod 34 is stopped from further advancementinto chamber 16 when control valve assembly 100 returns to the closedposition. This occurs when a sufficient length of piston rod 34 hasentered proximal compartment 198 such that the hydraulic fluid pressuretending to move control valve assembly 100 into the closed position,thereby precluding fluid travel through compression ports 118, isgreater than the external force applied to piston rod 34 which tends tocause the hydraulic fluid to move the control valve into the openposition.

As will be discussed below, in alternative embodiments the initialpressure within and the volume of distal compartment 196 can beselectively adjusted. The initial pressure and volume of distalcompartment 196 has a number of effects on the damping. For example, byincreasing the initial pressure within distal compartment 196, increasedforce is initially applied by the hydraulic fluid to maintain controlvalve assembly 100 in the closed position. As such, greater force topiston rod 34 is required to initially move control valve assembly 100into the open position.

Furthermore, having a higher initial pressure within distal compartment196 causes control valve assembly 100 to close earlier as piston rod 34is advanced into proximal compartment 198. That is, the gas pressurewithin distal compartment 196, and thus also the hydraulic fluidpressure within proximal compartment 198, increases exponentially as thevolume of distal compartment 196 is compressed. The increase in pressureis based on the compression ratio of distal compartment 196, i.e., thestarting volume of distal compartment 196 versus the final volume ofdistal compartment 196 when piston rod 34 is advanced into chamber 16.For example, if the starting volume of distal compartment 196 is 100 ccand the final volume is 25 cc, the compression ratio is 4:1. As aresult, the gas pressure and thus also the hydraulic fluid pressure inthe final volume is four times the gas pressure in the starting volume.The pressure continues to increase exponentially as the volume of distalcompartment 196 decreases by compression.

It is also appreciated that the starting volume of distal compartment196 can be adjusted separately from the initial pressure therein so asto separately effect the damping properties. For example, in a firstembodiment the initial volume of distal compartment 196 can be 100 ccwhile in a second embodiment the initial volume can be 75 cc. Assumingthe starting gas pressure in each embodiment is the same, the sameinitial force is applied to control valve 100 as discussed above.However, for the same advancement of piston rod 34 in each of theembodiments, the compression ratio for the second embodiment is greaterbecause the initial volume is smaller. As such, the rate of pressureincrease and resulting damping force is greater for the secondembodiment relative to the first embodiment.

In view of the foregoing, during a compressive movement of main piston102, a virtually infinite combination of pressures can be applied tocontrol valve assembly 100 as a result of: displacement of piston rod 34and the resulting pressure changes within chamber 16; varying bump loadsand resulting pressures that are generated within the chambers on eachside of main piston 102; and the resulting pressures that are variablygenerated upon distal face 134 of valve guide 104 and proximal face 148of control valve 106 through out the stroke of piston rod 34.

The resulting metering of hydraulic fluid flow through pressure ports118 on main piston 102 by control valve assembly 110 during acompressive movement of main piston 102 thus produces damping effectswhich are: position sensitive as a result of the position of piston rod34 within proximal compartment 198; variable position and load sensitivedepending on the position of main piston 102, speed/force of the bumpinput, and pressure within the distal compartment 196; and positionand/or load adjustable, by varying the volume and force of the pressurewithin distal compartment 196.

Depicted in FIG. 7, during rebound when piston rod 34 is being drawn outof chamber 16, the pressure applied by the hydraulic fluid keeps controlvalve assembly 100 closed, thereby preventing the hydraulic fluid thatis now proximal of control valve 106 from passing through compressionports 118. Rather, the hydraulic fluid flows through one of possiblythree rebound paths. In a first path, the hydraulic fluid enters reboundchannel 88 proximal of stop plate 174, travels centrally through pistonrod 34 along rebound channel 88, and then travels out through ports 79by distally flexing shims 84. In a second rebound path, rather thentraveling out through ports 79, the hydraulic fluid within reboundchannel 88 travels out through jet 80. In the third rebound path, thehydraulic fluid travels around the exterior of control valve 106 andenters pockets 120 of main piston 102. The hydraulic fluid then travelsout through rebound ports 122 by distally flexing shims 124.

By adjusting the stiffness and/or number of shims 84, 124 and the sizeof opening 82 in jet 80, the hydraulic fluid can simultaneously flowthrough one, two, or all three of the rebound paths. For example, byhaving shims 124 stiffer than shims 84, the hydraulic fluid may flowonly through jet 80 at low rebound forces. At a higher rebound force,the hydraulic fluid may flow through both the first and second reboundpath or through all three rebound paths.

The rebound force, typically produced by an opposing spring, isgenerally greatest when piston rod 34 is fully inserted into chamber 16(FIG. 6) and initially begins to move in the rebound direction. As such,all of the rebound paths may initially be used as piston rod 34 beginsto retract. However, as piston rod 34 continues to move in the rebounddirection, one or more of the rebound paths may close off, therebyslowing the rebound as piston rod 34 approaches the fully retractedposition. As will be discussed below with regard to alternativeembodiments, rebound channel 88 can also be selectively restricted orclosed so as to enable manual control of the hydraulic fluidtherethrough based on operating parameters.

As discussed above, the compressible gas is sealed within distalcompartment 196 so as to enable piston rod 34 to travel into chamber 16through the compression of the gas and to at least partially control theoperation of control valve assembly 100 by producing variable pressurethereon. It is appreciated, however, that there are a number ofalternative ways in which these same functions can be achieved.

For example, depicted in FIG. 8 a resiliently compressible member 246 isdisposed within distal compartment 196. Member 246 extends betweenfloating piston 184 and distal end wall 24. Although member 246 is shownas being a coiled spring, in alternative embodiments member 246 cancomprise other forms of mechanical springs or blocks of resilientlycompressible material such as rubber or polymeric foam. As the hydraulicpressure increases in proximal chamber 198, floating piston 184 slidesdistally resiliently compressing member 246. In this regard, compressedmember 246 functions similar to the compressed gas.

It is appreciated that member 246 can be used in addition to orindependent of filling distal compartment 196 with a gas at elevatedpressure. Where member 246 is independently used to provide thecompressive resistance, distal compartment 196 need not be sealed closedwithin housing 12. For example an opening depicted by dashed lines 248can be formed through distal end wall 24. Opening 248 facilitates properplacement of floating piston 184. In other embodiments, it isappreciated that member 246 need not be disposed within chamber 16 butcan be disposed outside of chamber 16. For example, a rod can extendfrom floating piston 184 through distal end wall 24 where it connectswith member 246 outside of housing 12.

In another alternative embodiment depicted in FIG. 9, a flexible bladder250 is disposed within the distal end of chamber 16. Bladder 250communicates with the exterior of housing 12 through a fill valve 252such as Schrader charge valve. Fill valve 252 enables bladder 250 to beselectively inflated with gas to a desired pressure. It is noted thatbladder 250 can be used in association with or independent of floatingpiston 184. That is, floating piston 184 can be eliminated so that thehydraulic fluid directly bears against inflated bladder 250 so as tocompress bladder 250. In this embodiment, bladder 250 bounds distalcompartment 196. Bladder 250 can also be filled with resilientlycompressible material such as rubber or polymeric foam.

Depicted in FIG. 10, floating piston 184 is replaced with a flexiblediaphragm 254. Diaphragm 254 is mounted to interior surface 14 ofsidewall 18 of housing 12 so as to divide chamber 16 into distalcompartment 196 and proximal compartment 198. A fill valve 256 is formedon sidewall 18 and enables distal compartment 196 to be filled with acompressible gas to a desired pressure. Again, as piston rod 34 isadvanced into chamber 16, the hydraulic fluid presses against diaphragm254 causing it to flex distally, thereby compressing the gas withindistal compartment 196.

It is appreciated that in other embodiments no mechanical barriers arerequired. For example, depicted in FIG. 11 chamber 16 is filled with agas 260, such as air, and a hydraulic fluid 262. A boundary line 264 isformed therebetween. As piston rod 34 enters chamber 16, hydraulic fluid262 compresses gas 260. In some uses, however, this embodiment is lessdesirable as the gas and hydraulic fluid can mix or emulsify withinchamber 16 and diminish operating properties.

Set forth below are a number of alternative embodiments of damperswherein like elements are identified by like reference characters. Inone embodiment of the present invention means are provided forselectively adjusting the size of distal compartment 196. By way ofexample, depicted in FIG. 12 is a damper 210. Damper 210 issubstantially identical to damper 10 except that damper 210 includes anadjusting piston 212 disposed within chamber 16 distal of floatingpiston 184. Adjusting piston 212 includes a peripheral side 214 having aseal 216 formed thereat. Seal 216 is biased in sealed engagement againstinterior surface 14 of sidewall 18 of housing 12 so as to enableadjusting piston 212 to selectively slide within chamber 16 withoutallowing fluid to pass through or around.

Centrally mounted on adjusting piston 212 is a sleeve 218. Sleeve 218has a threaded bore 220 which opens distally. In alternativeembodiments, it is appreciated that threaded bore 220 can be formeddirectly on the distal face of adjusting piston 212.

Mounted on housing 12 is a knob 222. Knob 222 has a first end with anenlarged head 224 formed thereat. Head 224 is at least partially exposedoutside of housing 12 so as to enable selective, manual rotation of head224. A threaded shaft 226 is formed at an opposing second end of knob222. Threaded shaft 226 is threadedly engaged with bore 220 on piston212. Accordingly, as depicted in FIGS. 12 and 13, by selectivelyrotating head 224 of knob 222, adjusting piston 212 is selectivelyadvanced and retracted within the distal end of chamber 16.

In this embodiment, distal compartment 196 is bounded between adjustingpiston 212 and floating piston 184. By manually advancing adjustingpiston 212 toward floating piston 184, distal compartment 196 becomessmaller. By making distal compartment 196 smaller, the gas pressure canbe increased therein and the rate at which the pressure increases withinproximal compartment 198 as floating piston 184 moves distallyincreases. Alternative embodiments of the means for selectivelyadjusting the size of distal compartment are discussed below.

Also mounted on housing 12 so as to communicate with distal compartment196 is a fill valve 228. As previously discussed, fill valve 228 cancomprise a conventional air valve such as used on car and bike tires.Fill valve 228 can thus be used to selectively increase or decreases thegas pressure within distal compartment 196. For example, air can beadded to or removed from distal compartment 196 so as to selectivelyincrease or decrease the gas pressure therein. Again, as previouslydiscussed, the gas pressure affects the operation of control valve 100and thus the movement of piston rod 34. Accordingly, adjusting piston212 and fill valve 228 enable an end user to selectively adjustdampening properties of damper 210 based on current or expectedoperating parameters.

In one embodiment of the present invention, means are provided forremotely adjusting the fluid pressure of the hydraulic fluid withinproximal compartment 198 of damper 10. By way of example and not bylimitation, depicted in FIG. 14 is one embodiment of a pressureregulated damping system 232. Dampening system 232 includes means forproviding a compressed gas. Examples of such means includes air source234 which can comprise a compressor or tank holding compressed gas.Damping system 232 further comprises a pressure regulator 235 and one ormore of dampers 10. A port 238 is provided in gas communication withdistal compartment 196 of each damper 10. Supply lines 240 provide gascommunication between air source 234 and pressure regulator 235. Inturn, supply lines 242, such as tubes or any other form of conduit,provide gas communication between pressure regulator 235 and distalcompartment 196 of each damper 10 by way of port 238.

Regulator 235 can be manually, electronically, and/or computercontrolled so as to selectively or automatically adjust the pressureindependently within distal compartment 196 of each damper 10 as theoperating environment for dampers 10 change. By increasing the pressurein distal compartment 196, the pressure differential is transferredthrough floating piston 184 so as to increase the fluid pressure of thehydraulic fluid within proximal compartment 198. In turn, increasing thehydraulic fluid pressure adjusts the operation of control valve 100 andthus the damping properties of damper 10. It is appreciated thatregulator 235 can come in a variety of different configurations and canbe comprised of multiple discrete components.

As one example of use, one or more dampers 10 can be incorporated intothe shock absorbers of an automobile or any other type of vehicle. Asroad and operating conditions change, for example, straight versuscurvy, on-road versus off-road, accelerating versus breaking, the rapidremote adjustment of the hydraulic fluid pressure can be used to provideoptimum suspension performance. It is appreciated that optimumperformance will often be obtain by simultaneously separately adjustingthe hydraulic fluid pressure in each of dampers 10 on a vehicle.

To facilitate automatic damping adjustment, one or more sensors 243,such as a gyroscopic sensor or other movement sensitive sensors, can bemounted on the vehicle and in electrical communication with a centralprocessing unit (CPU) 244. CPU 244 may be separate from or form aportion of regulator 235. Based on inputs from the one or more sensors243, CPU 244 can control regulator 235 so as to accordingly adjust thegas pressure and resulting hydraulic fluid pressure in one or more ofdampers 10 on the vehicle.

As an alternative to automatic adjustment, a manual input mechanism 245,such as a switch or control panel, can be electrically coupled with CPU244. Inputs provided to manual input mechanism 245 can be used to setthe hydraulic fluid pressure in each of dampers 10 to a predefinedvalve.

The use of gas pressure is only one example of the means for remotelyadjusting the fluid pressure of the hydraulic fluid within proximalcompartment 198 of damper 10. As an alternative embodiment, spring 246of FIG. 8 can be disposed between floating piston 184 and adjustingpiston 212 of FIG. 12. In turn, a motor or other form of gear mechanismis attached knob 222 in FIG. 12. Central processing unit 244 iselectrically coupled with the motor such that based on sensor or manualinput signals the motor adjusts the compression on spring 246 so as toremotely adjust the hydraulic fluid pressure in dampers 10.

It is appreciated that there are a variety of different systems that canbe used to remotely adjust the fluid pressure of the hydraulic fluidwithin dampers 10 by selectively adjusting the pressure applied tofloating piston 184 or one of the alternatives discussed thereto.

In view of the foregoing the suspension of a vehicle can be controlledby providing a vehicle having a suspension system including at least onepressure regulated damper; and automatically or selectively delivering agas to or withdrawing a gas from the at least one damper duringoperation of the vehicle so as to automatically or selectively controlsuspension performance properties of the at least one damper. Suchsuspension control can be performed during movement of the vehicle.

Likewise, suspension control can be obtained by automatically orselectively altering the fluid pressure of the hydraulic fluid withinthe at least one damper during operation of the vehicle so as toautomatically or selectively control suspension performance propertiesof the at least one damper, the automatic or selective altering of thefluid pressure being based on automatic sensor signals or manual inputsignals.

Depicted in FIG. 15 is another alternative embodiment of a damper 270incorporating features of the present invention. Damper 270 includeshousing 12 bounding chamber 16. Chamber 16 is divided by floating piston184 into distal compartment 196 and proximal compartment 198 whichcontain a compressed gas and hydraulic fluid, respectively. Again,floating piston 184 can be replaced with any of the alternatives aspreviously discussed.

A piston rod 272 slideably extends into the proximal end of housing 12.Piston rod 272 includes a base rod 278 and a bolt 280. Bolt 280 isscrewed onto the distal end face of base rod 278 so as to secure mainpiston 102 therebetween. Seal 114 is mounted on the peripheral side ofmain piston 102 and forms a slideable sealed biased engagement againstinterior surface 14 of sidewall 18.

Secured between an enlarged head 281 of bolt 280 and distal face 110 ofpiston 102 is a first shim 282. First shim 282 is biased against distalface 110 of piston 102 so as to cover the distal openings to reboundports 122. A second shim 284 is disposed between the distal end of baserod 278 and proximal face 108 of piston 102. Second shim 284 is biasedagainst proximal face 108 of piston 274 so as to cover the proximalopenings of compression ports 118. However, second shim 284 only coversa portion of pockets 120 leading to rebound ports 122. As previouslydiscussed with regard to shims 124 in FIG. 3, shims 282 and 284 functionas one-way check valves which control the direction of flow throughrebound ports 122 and compression ports 118, respectively. Thealternatives as previously discussed with regard to shims 124 are alsoapplicable to shims 282, 284, and the flexible shims disclosed in otherembodiments of the present invention.

In contrast to damper 10 wherein control valve assembly 100 is mountedto the moveable piston rod, in the present embodiment control valveassembly 100 is mounted on a secondary piston 274 disposed withinproximal compartment 198 between piston rod 272 and floating piston 184.Secondary piston 274 has the same configuration as main piston 102 andthus like reference characters are used to identify like elements. It isnoted, however, that secondary piston 274 and control valve assembly 100are rotated 180° relative to the corresponding structures in damper 10.As such, the proximal and distal orientations are reversed relativethereto.

Secondary piston 274 is secured in place by clips 292 which are receivedin grooves on interior surface 14 of sidewall 18 so as to bias againstopposing sides of secondary piston 274. In alternative embodiments,clips 292 can be further spaced apart to allow some longitudinal slidingof secondary piston 274. In yet other embodiments, secondary piston 274can be integrally formed with housing 12 so as to eliminate the need forseal 114 and clips 292. A shaft 288 extends through secondary piston 274and control valve assembly 100 so as to secure the two elementstogether. Shims 124 bias against proximal face 110 of secondary piston274 and are secured thereat by a head 290 of shaft 288 and washer 126.Stop plate 174 is mounted at the distal end of shaft 288 to control thedistal movement of control valve 106. The combination of secondarypiston 274, control valve 100 and stop plate 174 secured together byshaft 288 is herein referred to as base valve 286.

As depicted in FIG. 16, as piston rod 272 advances into distalcompartment 198 of chamber 16, the hydraulic fluid causes second shims284 to proximally flex allowing the hydraulic fluid to travel throughcompression ports 118 of main piston 102. Simultaneously, the hydraulicfluid also moves control valve 106 of control valve assembly 100 into anat least partially open state so that the hydraulic fluid can passthrough compression ports 118 of secondary piston 274. The hydraulicfluid then pushes floating piston 184 distally, thereby compressing thegas within distal compartment 196.

Depicted in FIG. 17, when the compressive movement of piston rod 272 hasstopped within chamber 16, the fluid pressure within proximalcompartment 198 collapses valve chamber 170, thereby moving controlvalve 106 into the closed position. As depicted in FIG. 18, during therebound stroke the hydraulic fluid travels through secondary piston 274by flowing through pockets 120 and out through rebound ports 122 byproximally flexing shims 124. Similarly, the hydraulic fluid travelsthrough main piston 102 by traveling through pockets 120 and out throughrebound ports 122 by distally flexing shims 282.

Depicted in FIG. 19 is another alternative embodiment of a damper 300.Damper 300 includes a double tube housing 302. Specifically, housing 302comprises a distal cap 304 and an opposing proximal cap 306. Extendingbetween caps 304 and 306 and secured thereto is an outer tube 308.Disposed within outer tube 308 is an inner tube 310 which also extendsbetween opposing caps 304 and 306. Inner tube 310 has an interiorsurface 312 that bounds an inner compartment 314. Bounded between theexterior surface of inner tube 310 and the interior surface of outertube 308 is an outer compartment 316. Inner compartment 314 communicateswith outer compartment 316 through a port 318.

Inner compartment 314 is filled with a hydraulic fluid. Disposed withinouter compartment 316 is an inflatable bladder 320. Bladder 320 isselectively inflated through a fill valve 322 projecting through outertube 308. Disposed within the distal end of inner compartment 314 isbase valve 286 as previously discussed with regard to damper 270 inFIGS. 15-18. In this embodiment, however, shaft 288 is used to securebase valve 286 directly to distal end cap 304. It is appreciated thatalternative mounting methods can be used to secure base valve 286 withininner tube 310. Piston rod 272 with main piston 102, as also discussedwith damper 270, are slideably disposed within inner compartment 314.

As depicted in FIG. 20, damper 300 operates similar to damper 270.Specifically, as piston rod advances into inner compartment 314, controlvalve 106 moves to the open position and the hydraulic fluid travelsthrough compression ports 118 on both main piston 102 and secondarypiston 274. As the fluid passes secondary piston 274, the hydraulicfluid enters outer compartment 316 thorough port 318 where it compressesbladder 320. The hydraulic fluid continues to compress bladder 320 untilpiston rod 272 is retracted. During retraction, the hydraulic fluidflows back through main piston 102 and secondary piston 274 insubstantially the same ways as previously discussed with regard todamper 270. In an alternative embodiment, it is appreciated that bladder320 can be replaced with a floating piston which encircles inner tube310 and slides within outer compartment 316. In yet another alternative,damper 320 can be inverted and bladder 320 removed. In this embodiment,a gas, such as air, is trapped within outer compartment 316. Thehydraulic fluid directly contacts the gas, such as previously discussedwith regard to FIG. 11, so as to selectively compress the gas.

Depicted in FIG. 21 is one embodiment of shock absorber 350incorporating features of the present invention. As depicted in FIGS. 22and 23, shock absorber 350 comprises a piggy-back housing 352 whichincludes a primary tube 354, a secondary tube 356 and a stem 358extending therebetween. As depicted in FIG. 24 primary tube 354 has aninterior surface 430 bounding a primary chamber 432 while secondary tube356 has an interior surface 437 bounding a secondary chamber 438.Returning to FIGS. 22 and 23, stem 358 has a substantially U-shapedconfiguration that extends between a first end 359 and an opposingsecond end 361. An opening 357 extends through stem 358 at first end 359for selective attachment to a structure.

Primary tube 354 has an exterior surface 360 extending between a distalend 362 and an opposing proximal end 364. Distal end 362 of primary tube354 is threaded into first end 359 of stem 358. A proximal end cap 366is threaded into proximal end 364 of primary tube 360. Adjustablythreaded onto distal end 362 of primary tube 360 is an annular distalspring retention collar 368.

A piston rod 370 has a distal end 372 (FIG. 24) and an opposing proximalend 374. A bracket 376 having an opening 378 extending therethrough isthreaded onto proximal end 374 of piston rod 370. Positioned on bracket376 is an annular proximal spring retention collar 380. A coiled spring382 extends between distal spring retention collar 368 and proximalspring retention collar 380. The tension on spring 382 is selectivelyadjusted by adjusting distal spring retention collar 368 along thelength of primary tube 354.

Encircling piston rod 370 between proximal end cap 366 and proximalspring retention collar 380 is a bottom-out cushion 382. Cushion 382 ismade of a resiliently flexible material such as rubber or polymericfoam.

As depicted in FIG. 24, piston rod 370 includes a tubular base rod 384and bolt 44 as previously discussed with regard to damper 10. Base rod384 has an interior surface 390 bounding a channel 392 thatlongitudinally extends between a distal end 386 and an opposing proximalend 388. Bolt 44 is threaded onto distal end 386 of base rod 384 so thatchannel 78 of bolt 44 is in fluid communication with channel 392 of baserod 384. A port 394 extends through base rod 384 so as to provide fluidcommunication between primary chamber 432 of primary tube 354 andchannel 78. A pin 396 is slideably disposed within channel 392 of baserod 384. Pin 396 has a tapered nose 398 disposed at the distal endthereof. Nose 398 is configured to complementary fit within the proximalopening of channel 78 of bolt 44. As a result, pin 396 can be used toselectively restrict or close off fluid communication between primarychamber 432 and channel 78 by advancing and retracting pin 396 withinbase rod 384.

Bracket 376 has a distal end face 410 having a bore 412 recessedthereon. A passageway 400 transversely extends across bracket 376 so asto intersect with bore 412. Bracket 376 is screwed onto base rod 384such that pin 396 extends down through bore 412 and partially intopassageway 400. A regulator 414 is adjustably disposed within passageway400. Regulator 414 includes a shaft 416 having a distal portion 418 inthreaded engagement within passageway 400 of bracket 376, asubstantially frustuconical transition portion 420, and a substantiallycylindrical central portion 422 formed therebetween. Regulator 414 alsoincludes a selectively removable knob 424. Selective rotation of knob424 advances and retracts regulator 414 within passageway 400. Asregulator 414 is advanced within passageway 400, frustuconicaltransition portion 420 biases against the distal end of pin 396 causingpin 396 to advance toward bolt 44, thereby restricting or closing offthe proximal opening to channel 78. In turn, as regulator 414 isretracted, pin 396 is lowered, thereby opening the flow path to channel78. Alternative adjustment systems may also be used to move pin 396.

Mounted on the distal end of piston rod 370 is main piston 102, controlvalve assembly 100, and stop plate 174. These elements are substantiallythe same as previously discussed with regard to damper 10 and operate inthe same manner. The only distinction is that control valve assembly 100of the embodiment shown in FIG. 24 has a slightly different configuredvalve chamber 170. This is due to different grooves formed on valveguide 104 and control valve 106.

Formed at first end 359 of stem 358 is a threaded bore 446. Distal end362 of primary tube 360 is threaded within bore 446. A threaded sleeve450 projects from an end face 451 at second end 361 of stem 358. Athreaded central bore 453 is formed on end face 451. The distal end ofsecondary tube 356 is coupled with threaded sleeve 450. Alternativeattachment methods may also be used to secure primary tube 360 andsecondary tube 356 to piggy back housing 352, including use of a 1-pieceforged or cast assembly which includes all of the aforementioned parts.

Stem 358 is configured to provide fluid communication between primarychamber 432 of primary tube 360 and secondary chamber 438 of secondarytube 356. Specifically, a transition channel 448 communicates with bore446 at first end 359 of stem 358. As depicted in FIG. 25, a first valvechamber 452 and a second valve chamber 454 are each bored into stem 358from second end 361 toward first end 359. A first pathway 456 extendsfrom first valve chamber 452 to transition channel 448 while a secondpathway 458 extends from second valve chamber 454 to transition channel448. A bore 460 intersects with first valve chamber 452 and extends toend face 451 at second end 361 of stem 358. A bore 462 transverselyintersects with both second valve chamber 454 and central bore 453 so asto provide fluid communication therebetween. A plug 463 is secured inthe opening of bore 462 to prevent fluid from escaping thereat.

A first valve 466 is adjustably disposed within first valve chamber 452.First valve 466 comprises a head 468 having a socket 470 formed on theend thereof to selectively receive a tool for rotating first valve 466.First valve 466 also has a central body 472 having threads thereon thatengage with the inner wall of first valve chamber 452. One or more seals474 encircle body 472 and provide sealed engagement with the inner wallof first valve chamber 452. Projecting from body 472 is a shaft 474having a tapered nose 476. Tapered nose 476 is configured to selectivelyengage with the opening to first pathway 456. Accordingly, byselectively rotating first valve 466, shaft 474 advances or retracts soas to selectively restrict or open the opening to first pathway 456.

A second valve 480 is adjustably disposed within second valve chamber454. Similar to first valve 466, second valve 480 comprises head 468,threaded body 472, and seal 474. A piston 482 is movably disposed withinsecond valve chamber 454 at the opening to second pathway 458. A spring484 extends between body 472 and piston 482 so as to bias piston 482against the opening to second pathway 458. A rod 486 extends from piston482, centrally through spring 484, and freely into a channel 487 formedin the end of body 472. As piston 482 is pushed back, rod 486 is free toretract within body 472.

By advancing second valve 480 within second valve chamber 454, spring484 is compressed, thereby providing greater biasing force againstpiston 482. Second pathway 458 is thus only open when sufficient forceis applied to piston 482 to overcome the applied spring force.Accordingly, by selectively adjusting first valve 466 and second valve480, dampening properties can be adjusted for operating conditions.

Returning to FIG. 24, movably disposed within secondary chamber 438 is afloating piston 490. Floating piston 490 divides the enclosed areabounded by primary tube 354, secondary tube 356 and stem 358 into aproximal compartment 492 and a distal compartment 493. Again, proximalcompartment 492 is filled with a hydraulic fluid while distalcompartment 493 is filled with a compressible gas. Other alternatives aspreviously discussed can also be used to replace or use in conjunctionwith floating valve 490 and the compressible gas.

Turning to FIG. 26, a tubular bolt 508 having an enlarged head 509 isthreaded into central opening 453 at second end 361 of stem 358. Tubularbolt 508 has an interior surface 510 bounding a channel 512. Centralopening 453 and channel 512 provide fluid communication between secondvalve chamber 454 and secondary chamber 438. Alternative attachmentmethods may be used in place of bolt 508.

Encircling bolt 508 and biased against the interior surface of sleeve450 is a fixed piston 494 having a configuration similar to piston 102as discussed with damper 10. Fixed piston 494 has a proximal face 496and an opposing distal face 498. Extending between faces 496 and 498 area plurality of radially spaced apart damping ports 500. A plurality ofradially spaced apart pockets 502 are recessed on proximal face 496. Acompression port 504 extends from distal face 498 to each pocket 502.

A first shim 514 encircles bolt 508 and biases against proximal face496. First shim 514 covers the proximal opening of damping ports 500 butonly covers a portion of pockets 502. A washer 516 encircles bolt 508and is disposed between shim 514 and end face 451 of stem 358. Washer516 provides spacing between end face 451 and first shim 514 so thatfirst shim 514 can flex proximal during operation.

A second shim 518 encircles bolt 508 and biases against distal face 498of fixed piston 494. Second shim 518 covers the distal opening ofcompression ports 504 but only covers a portion of the distal openingsof damping ports 500. A washer 520 is disposed between bolt head 509 andsecond shim 518 to enable second shim 518 to flex distally duringoperation. As previously mentioned, bore 460 extends between first valvechamber and end face 451 of stem 358. As such, the hydraulic fluidpassing through bore 460 must necessarily pass through fixed piston 494as it enters secondary chamber 438.

Depicted in FIG. 24, threaded into the distal end of secondary tube 356is a volume adjuster assembly 520. Depicted in FIG. 27, volume adjusterassembly 520 comprises an annular sleeve 522 having an interior surface528 and an exterior surface 526. Sleeve 522 is threaded into the distalend of secondary tube 356. Adjustably threaded into sleeve 522 is atubular stem 530. Stem 530 has a proximal end 532 and a distal end 534.Mounted on proximal end 532 of stem 530 so as to encircle and radiallyoutwardly project therefrom is a piston 536. Piston 536 is secured tostem 530 by a clip 538 mounted on stem 530 proximal of piston 536.Piston 536 outwardly projects so as to seal in slideable engagementagainst interior surface 437 of secondary tube 356. Distal compartment493 is bounded between floating piston 490 and piston 536. Byselectively rotating stem 530 relative to sleeve 522, stem 530 and thuspiston 536 advance or retract relative to sleeve 522. Thus by advancingstem 530 and piston 536, distal compartment 493 becomes smaller. In turnthe rate at which the gas compresses, i.e., the compression ratio,within distal compartment 493 increases.

A cavity 540 is recessed on a distal end face 541 of stem 530. Apassageway 542 extends from cavity 540 to a proximal end face 544 ofstem 530. Positioned within cavity 540 in communication with passageway542 is a fill valve 546 through which pressured gas can be fed intodistal compartment 493. One example of valve 546 is a Schrader chargevalve. Thus, fill valve 546 can be used to selectively adjust the gaspressure within distal compartment 493, thereby adjusting the relateddampening properties.

It is appreciated that shock absorber 350 operates using the sameprincipals as discussed in detail with regard to the other embodiments.

Depicted in FIG. 28 is another alternative embodiment of a damper 550.Damper 550 has a piggy-back housing 552 comprising a primary housing554, a secondary housing 556, and a tubular stem 558 extendingtherebetween. A sealed hose, pipe, or other conduit may be substitutedfor stem 558 for establishing fluid communication between primaryhousing 554 and secondary housing 556. Primary housing 554 is the sameas housing 12 previously discussed with regard to damper 10 except forthe attachment of stem 558. Furthermore, as also discussed with damper10, coupled with primary housing 554 is piston rod 34 having a mainpiston 102, control valve assembly 100, and stop plate 174 mountedthereon. As such like elements between damper 550 and damper 10 areidentified by like reference characters.

Secondary housing 556 comprises a tubular, cylindrical sidewall 560extending between a proximal end 562 to an opposing distal end 564.Proximal end 562 terminates at a proximal end wall 563. Threadedlydisposed within distal end 564 of secondary housing 556 is volumeadjuster assembly 520 as previously discussed with regard to FIG. 25.Alternative methods for attaching volume adjustor assembly 520 can beused. Sidewall 560 has an interior surface 566 that bounds a secondarychamber 568 extending between proximal end wall 563 and piston 536 ofvolume adjuster assembly 520. Tubular stem 558 bounds a channel 576 thatextends between primary chamber 16 and secondary chamber 568. Primarychamber 16, secondary chamber 568, and channel 576 of stem 558 combineto form a total chamber 578.

Inwardly projecting from sidewall 560 at proximal end 562 of secondaryhousing 556 is a retaining wall 570. Slideably disposed within secondarychamber 568 distal of retaining wall 570 is a floating piston 574.Floating piston 574 divides total chamber 578 into a proximalcompartment 580 and a distal compartment 582. Proximal compartment 580is filled with a hydraulic fluid while distal compartment 582 is filledwith a compressible gas.

Disposed between retaining wall 570 and proximal end wall 563 ofsecondary housing 556 is a base valve 586. Depicted in FIG. 29 is anenlarged cross sectional view of base valve 586. As depicted therein,base valve 586 comprises a secondary piston 584 having compression ports118 and rebound ports 122 extending therethrough. A tubular shaft 583extends through secondary piston 584 and beyond the proximal facethereof. A washer 585 encircles shaft 583 so as to cover the openings torebound ports 122 while leaving the openings to compression ports 118open. A retention collar 587 is threaded onto the proximal end of shaft583. A spring 588 extends between retention collar 587 and washer 585 soas to bias washer 585 against the openings to rebound ports 122. Washer585 and spring 588 function as a one-way check valve to regulate thefluid flow through rebound ports 122 and are an alternative embodimentto the flexible shims as discussed in other embodiments.

Disposed against the distal face of secondary piston 584 and encirclingtubular shaft 583 is control valve assembly 100. Control valve assembly100 controls the fluid flow through compression ports 118 insubstantially the same method of operation as discussed in the otherembodiments. That is, based on the force of the fluid passing throughcompression ports 118 and the pressure of the hydraulic pressure,control valve assembly 100 is moved to some extent between the openposition shown in FIG. 30 and the closed position shown in FIG. 31.Unlike the prior embodiments, however, control valve assembly 100 can beselectively adjusted through the application of a spring force.

Specifically, a collar 589 is inserted within secondary housing 556.Collar 589 encircles tubular shaft 583 so that an annular spring cavity591 is formed therebetween. Disposed within spring cavity 591 is anannular first bias plate 592 disposed against control valve 106 and anannular second bias plate 593 disposed against a portion of collar 589.A spring 594 extends between bias plates 592 and 593 so as to bias firstbias plate 592 against control valve 106. Posts 595 extend from secondbias plate 593 to an end cap 596. End cap 596 is configured such thatrotation of end cap 596 causes posts 595 to advance into spring cavity591, thereby further compressing spring 594. As spring 594 is compressedgreater force is applied to control valve 106, thereby altering theoperation thereof.

To enable the hydraulic fluid to access the distal side of control valveassembly 100, a fluid path 597 extends through shaft 583 andcommunicates with spring cavity 591 and chamber 581. Ports 598 areformed on first bias plate 592 so as to enable the hydraulic fluid todirectly contact control valve assembly 100. The hydraulic fluid thusassists in the opening and closing of control valve assembly 100 of basevalve 586 based on the pressure of the hydraulic fluid. To selectivelycontrol the flow of hydraulic fluid into and out of spring cavity 591and chamber 581, a pin 599 is threadedly disposed within fluid path 597so as to selectively constrict fluid path 597.

FIG. 30 shows the flow path of the hydraulic fluid as piston rod 34 isadvanced within primary chamber 16. FIG. 31 shows the flow path of thehydraulic fluid as piston rod 34 is retracted out of primary chamber 16.

Depicted in FIG. 32 is a damper 600 that is substantially identical todamper 550. Damper 600 is distinguished over damper 550 in that floatingpiston 574 has been replaced with a flexible diaphragm 602.

Depicted in FIG. 33 is another alternative embodiment of a damper 610that is similar to damper 550. Damper 610 is distinguished over damper550 in that base valve 586 which contains a control valve assembly 100has been replaced with a conventional base valve 612 that does notincorporate a control valve assembly 100.

Depicted in FIGS. 34 and 35 is one embodiment of how an inventive dampercan be incorporated into a front fork of a bicycle, motorcycle, or thelike. Specifically, depicted in FIG. 34 is a front fork 630 having anupper tube 632 slideably received within a lower tube 634. Disposedwithin lower tube 634 so as to resiliently bias against upper tube 632is a spring 633. Spring 633 provides the rebound force for the damperand can be positioned at different locations. Alternative methods ofproducing a rebounding force may also be used, i.e., compressed gas,microcellular foam, and the like. Disposed within upper tube 632 is atubular cartridge 636 which bounds a chamber 638. A tubular piston rod640 has a proximal end 642 mounted on a base floor of lower tube 634 andan opposing distal end 644 slideably extending up through upper tube 632and cartridge 636. Mounted within chamber 638 on distal end 644 ofpiston rod 640 is main piston 102, control valve 100, and stop plate 174as previously discussed with regard to damper 10 in FIGS. 1-7.

Rebound channel 88, as disclosed with regard to damper 10, is alsoformed on piston rod 640 so as to extend between opposing sides of mainpiston 102. In contrast to rebound channel 88 for damper 10, however, inthe embodiment depicted in FIG. 34 a regulating pin 641 having a taperednose is movably disposed within piston rod 640. That is, by selectivelyrotating regulating pin 641 outside of lower tube 634, pin 641 can beadjusted to selectively restrict the flow of hydraulic fluid throughrebound channel 88. In part, the slower the flow of hydraulic fluidthrough rebound channel 88, the slower the rebound of piston rod 640.

Screwed into the distal end of cartridge 636 is a hollow sleeve 646. Inturn, screwed into sleeve 646 is an end plug 648 having a stem 650proximally projecting therefrom within chamber 638. A first piston 652encircles and is slideably disposed on stem 650. First piston 652 formsa sealed engagement with stem 650 and cartridge 636. As such, firstpiston 652 forms a barrier that divides chamber 638 into a relativeproximal chamber 654 and a relative distal chamber 656. Proximal chamber654 is filled with a hydraulic fluid while distal chamber 656 is filledwith a compressible gas such as air.

Mounted against end plug 648 so as to also encircle stem 650 is a secondpiston 660. Second piston 660 is also in sealed engagement with stem 650and cartridge 636. By rotating end plug 648, second piston 660 advancesinto distal chamber 656 effectively decreasing the size of distalchamber 656. This also increases the pressure within both proximalchamber 654 and distal chamber 656 and the compression ratio withindistal chamber 656.

A fill valve 662 is mounted on end plug 648. A passageway 664 extendsthrough end plug 648 from fill valve 662 to distal chamber 656. As such,fill valve 662 can be used to selectively adjust the volume and pressureof gas within distal chamber 656.

Finally, although not required, a base valve piston 668 is rigidlydisposed within proximal chamber 654 between first piston 652 and pistonrod 640. Base valve piston 668 is sealed against cartridge 636 and,except for having a solid center, has substantially the sameconfiguration as main piston 102. Specifically, base valve piston 668has compression ports 118 and rebound ports 122 extending therethrough.Flexible shims 670 and 672 are mounted on opposing sides of base valvepiston 668, as previously discussed in other embodiments, to control theflow of hydraulic fluid through compression ports 118 and rebound ports122, respectively. Base valve piston 668 thus further controls the flowof hydraulic fluid and transfer of pressure which partially controls thedamping properties.

FIG. 35 shows front fork 630 with piston rod 640 being advanced intochamber 638.

The use of cartridge 636 as discussed above with regard to front fork630 is for ease in manufacture and assembly. The use of cartridge 636also enables the dampers of the present invention to be retrofit intoexisting forks. Depicted in FIG. 36, however, is a front fork 676. Frontfork 676 is the same as front fork 630 except that cartridge 636 hasbeen removed. FIG. 37 shows front fork 676 with piston rod 640 beingadvanced into chamber 638 while FIG. 38 shows front fork 676 with pistonrod 640 being withdrawn from chamber 638.

It is appreciated that all of the different damping configurationsdisclosed herein can be incorporated in a front fork. As a furtherexample, depicted in FIGS. 39 and 40 is a front fork 680 where controlvalve 100 has been moved from main piston 102 to base valve piston 668.This system operates similar to the damper discussed with regard toFIGS. 15-18.

The above discussed dampers of the present invention provide automaticadjustment of damping properties based on operating conditions, therebyoptimizing damping. Different embodiments provide for a variety ofselective manual damping adjustments and/or remote damping adjustments.Such adjustability enables the dampers to be effectively used in avariety of different conditions and on a variety of different vehicle orother systems. The design of the dampers also facilitates ease inmanufacture and assembly.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example,disclosed herein are numerous examples of different dampers havingdifferent features for controlling damping properties. It isappreciated, however, that the different features can be mixed andmatched so as to form a variety of other unique assemblies. Accordingly,the described embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A suspension damper comprising: a housingbounding a main chamber, the main chamber comprising a first compartmentand a second compartment; hydraulic fluid disposed within the first andsecond compartments of the main chamber; a piston rod selectivelymovable between an advanced position wherein a portion of the piston rodis advanced into the main chamber and a retracted position wherein theportion of the piston rod is retracted from the main chamber, wherein asthe piston rod is moved from the retracted position to the advancedposition fluid pressures of the hydraulic fluid within the first andsecond compartments of the main chamber both progressively increase anda portion of the hydraulic fluid passes from the first compartment tothe second compartment through a passage within the housing; and acontrol valve at least partially disposed within the main chamber, thecontrol valve at least partially bounding a gas chamber, the controlvalve being in pressure communication with the hydraulic fluid in boththe first and second compartments so that the control valve generatesresistance to the flow of the hydraulic fluid through the passage whichresistance varies as the piston rod advances into the main chamberaccording to the pressure difference between a pressure within the gaschamber and the fluid pressure of the hydraulic fluid in the secondcompartment.
 2. The suspension damper as recited in claim 1, furthercomprising a stationary piston rigidly secured to or integrally formedwith the housing, the stationary piston at least partially bounding thepassage through which the hydraulic fluid flows.
 3. The suspensiondamper as recited in claim 1, further comprising a resilient forcepushing against the control valve in opposition to the fluid pressure ofthe hydraulic fluid in the first compartment acting against the controlvalve.
 4. The suspension damper as recited in claim 1, furthercomprising a spring biased against the control valve so as to produce aresilient force acting against the control valve in opposition to thefluid pressure in the first compartment acting against the controlvalve.
 5. The suspension damper as recited in claim 1, furthercomprising a compressed gas pushing against the control valve so as toproduce a resilient force acting against the control valve in oppositionto the fluid pressure in the first compartment acting against thecontrol valve.
 6. The suspension damper as recited in claim 1, whereinthe control valve is mechanically separated from the piston rod so thatmovement of the piston rod does not directly move the control valve butrather movement of the piston rod moves the control valve as a result ofchanging the fluid pressures of the hydraulic fluid in the first andsecond compartments.
 7. The suspension damper as recited in claim 1,wherein the control valve is longitudinally spaced apart from the pistonrod so that the control valve does not encircle the piston rod.
 8. Thesuspension damper as recited in claim 1, further comprising a valveguide disposed adjacent to the control valve so that the gas chamber isat least partially formed between the control valve and the valve guide,the gas chamber being sealed from the hydraulic fluid, a gas beingdisposed within the gas chamber.
 9. The suspension damper as recited inclaim 1, further comprising a barrier disposed within the main chamberthat divides the main chamber into a relative first chamber and arelative second chamber, the barrier preventing the transfer of fluidsor gasses between the first chamber and the second chamber but enablingthe transfer of pressure between the first chamber and the secondchamber, a portion of the piston rod being disposed within the firstchamber.
 10. The suspension damper as recited in claim 9, wherein thebarrier comprises a floating piston.
 11. The suspension damper asrecited in claim 9, wherein the barrier comprises a bladder.
 12. Thesuspension damper as recited in claim 9, further comprising a gas valvemounted on the housing for selectively putting a gas into or withdrawinga gas from the second chamber.
 13. The suspension damper as recited inclaim 9, further comprising means for selectively adjusting the size ofthe second chamber.
 14. The suspension damper as recited in claim 1,wherein the housing comprises: a primary housing bounding a primarychamber; a secondary housing spaced apart from the primary housing, thesecondary housing bounding a secondary chamber; and a fluid pathwayfluid coupling the primary chamber to the secondary chamber.
 15. Thesuspension damper as recited in claim 14, wherein the piston rod ispartially disposed within the primary chamber and the control valve isat least partially disposed within the fluid pathway or the secondarychamber.
 16. A suspension damper comprising: a housing comprising: aprimary housing bounding a primary chamber; a secondary housing boundinga secondary chamber, the secondary housing being spaced apart from theprimary housing; and a fluid pathway extending between the primarychamber and the secondary chamber; hydraulic fluid disposed within atleast a portion of the primary chamber, the secondary chamber, and thefluid pathway; a piston rod coupled to the primary housing andselectively movable between an advanced position wherein a portion ofthe piston rod is advanced into the primary chamber and a retractedposition wherein the portion of the piston rod is retracted from theprimary chamber, wherein as the piston rod is moved from the retractedposition to the advanced position fluid pressures of the hydraulic fluidwithin the primary and secondary chambers both progressively increaseand a portion of the hydraulic fluid passes through a passage within thehousing between the primary and secondary chambers; and a control valveat least partially disposed within the secondary chamber or the fluidpathway, the control valve at least partially bounding a gas chamber,wherein a pressure within the gas chamber and the fluid pressure of thehydraulic fluid within the primary chamber each exert a force tending toopen the control valve, and the fluid pressure of the hydraulic fluid inthe secondary chamber exerts a force tending to close the control valve.17. The suspension damper as recited in claim 16, wherein the housingcomprises a piggy back housing having a substantially U-shapedconfiguration, a stem extending from the primary housing to thesecondary housing and bounding the fluid path.
 18. The suspension damperas recited in claim 16, wherein the primary housing has a centrallongitudinal axis and the secondary housing has a central longitudinalaxis that is offset from the central longitudinal axis of the primaryhousing.
 19. The suspension damper as recited in claim 16, furthercomprising a stationary piston rigidly secured to or integrally formedwith the housing, the stationary piston at least partially bounding thepassage through which the hydraulic fluid flows.
 20. The suspensiondamper as recited in claim 16, further comprising a spring resilientlybiased against the control valve, the spring exerting another forcetending to close the control valve.
 21. The suspension damper as recitedin claim 1, wherein the fluid pressure of the hydraulic fluid in thefirst compartment provides a force tending to open the control valve andthe fluid pressure of the hydraulic fluid in the second compartmentprovides a force tending to close the control valve.
 22. The suspensiondamper as recited in claim 1, wherein the control valve is disposedbetween the first and second compartments of the main chamber.
 23. Thesuspension damper as recited in claim 1, wherein the control valve abutsthe first compartment, the second compartment, and the valvecompartment.
 24. The suspension damper as recited in claim 1, whereinthe control valve at least partially radially encircles the valvecompartment.
 25. The suspension damper as recited in claim 1, whereinthe control valve allows more hydraulic fluid to flow through thepassage when the piston rod is in the retracted position than when thepiston rod is in the advanced position when an identical advancing forceis placed on the piston rod in both positions.
 26. A suspension dampercomprising: a housing bounding a main chamber, the main chambercomprising a first compartment and a second compartment; hydraulic fluiddisposed within the first and second compartments of the main chamber; apiston rod selectively movable between an advanced position wherein aportion of the piston rod is advanced into the main chamber and aretracted position wherein the portion of the piston rod is retractedfrom the main chamber, wherein as the piston rod is moved from theretracted position to the advanced position fluid pressures of thehydraulic fluid within the first and second compartments of the mainchamber both progressively increase and a portion of the hydraulic fluidpasses between the first and second compartments through a passagewithin the housing; and a control valve at least partially disposedwithin the main chamber, the control valve at least partially bounding agas chamber, wherein: a gas pressure within the gas chamber and thefluid pressure of the hydraulic fluid within the first compartment eachexert a force tending to open the control valve, and the fluid pressureof the hydraulic fluid within the second compartment exerts a forcetending to close the control valve.
 27. A suspension damper comprising:a housing bounding a main chamber, the main chamber comprising a firstcompartment and a second compartment; hydraulic fluid disposed withinthe first and second compartments of the main chamber; a piston rodselectively movable between an advanced position wherein a portion ofthe piston rod is advanced into the main chamber and a retractedposition wherein the portion of the piston rod is retracted from themain chamber, wherein as the piston rod is moved from the retractedposition to the advanced position fluid pressures of the hydraulic fluidwithin the first and second compartments of the main chamber bothprogressively increase and a portion of the hydraulic fluid passesbetween the first and second compartments through a passage within thehousing; and a control valve at least partially disposed within the mainchamber, the control valve at least partially bounding a gas chamber,wherein the fluid pressures of the hydraulic fluid in the first andsecond compartments exert opposing opening and closing forces on thecontrol valve, and a gas pressure of the gas chamber exerts a thirdforce on the control valve.